Determining the role of the phytotoxic secondary metabolite rubellin D in the pathology of Ramularia collo-cygni, the fungus responsible for Ramularia leaf spot disease of barley

The non-host specific phytotoxin rubellin D is produced by the pathogenic fungus Ramularia collo-cygni, the agent responsible for Ramularia leaf spot (RLS), an important disease of barley (Hordeum vulgare) in northern Europe. Development of RLS symptoms in crops has been associated with the release and action of phytotoxins such as rubellin D in the host plant despite no supporting evidence of this interaction. Here, we infiltrated leaves of barley landraces with rubellin D to investigate the link between RLS and this phytotoxin. Results suggest that rubellin D sensitivity and RLS susceptibility may not be directly linked but other factors might determine the outcome of the interaction between barley and R. collo-cygni. Research using the model plant Arabidopsis thaliana to determine the mode of action of rubellin D in planta is on-going.